Comprehensive Income Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	$ 0	$ 0	$ (224)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	8	7	34
Other Comprehensive Income (Loss), before Tax	(370)	2,071	(1,329)
Other Comprehensive Income (Loss), Tax	335	(933)	523
Other Comprehensive Loss	(35)	1,138	(806)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Schedule of Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	(1,505)	(1,672)	(3,017)
Other Comprehensive Income (Loss), Available-for-sale Securities, before Reclassification Adjustments, Tax	565	648	1,185
Reclassification from AOCI, Current Period, Tax	(111)	(9)	51
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(940)	(1,024)	(1,832)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	448	22	(129)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	337	13	(78)
Other Comprehensive Loss	(603)	(1,011)	(1,910)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Schedule of Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax	287	3,017	1,395
Reclassification from AOCI, Current Period, Tax	(49)	(281)	(332)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	214	1,721	848
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	411	716	846
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	362	435	514
Other Comprehensive Income (Loss) before Reclassifications, Tax	(73)	(1,296)	(547)
Other Comprehensive Loss	576	2,156	1,362
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member]
Schedule of Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, before Tax			(368)
Reclassification from AOCI, Current Period, Tax	3	5	22
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0	(224)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(11)	(12)	(56)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(8)	(7)	(34)
Other Comprehensive Income (Loss) before Reclassifications, Tax			144
Other Comprehensive Loss	$ (8)	$ (7)	$ (258)